As a forging die device for manufacturing engine valves by extrusion-forging, there is one shown in the following Patent Document 1. The forging die device in the following Patent Document 1 is to gradually form a stem portion W1 of an engine valve by extrusion-forging of a material W from a molding land 3 provided at the bottom portion of a cavity 2 by utilizing a punch 20. The stem portion W1 is knocked out of the molding land 3, thereby causing a stem curve to right or left from the central shaft line of the stem portion W1 in the tip end of the stem portion W1 as molding progresses. However, because there is an inner diameter greater than an outer diameter of the stem portion W1 in the forging die, and a clearance portion 4 extending in the molding direction of the stem portion W1 is provided therein, the stem portion W1 extends without coming into contact with the inner wall of the forging die even when a stem curve is caused. On the other hand, a knock-out pin 30 which moves forward and backward inside a capture portion 5 is provided in the vicinity of an end position of molding an engine valve, and the tip end of the stem portion W1 comes into contact with a sloping portion 6 to be guided to the capture portion 5 at the last minute of completion of the molding. The molded engine valve whose tip end is pressed by the knock-out pin 30 so as to be held by the capture portion 5, to be taken out of the forging die.